Lanthanide(iii) complexes of monophosphinate/monophosphonate DOTA-analogues: effects of the substituents on the formation rate and radiolabelling yieldElectronic supplementary information (ESI) available: Crystal packing of EuIII-do3aPH, molecular structure of do3a-lactame, experimental data of crystal structures, overall protonation constants, absorption spectra of CeIII complexes, formation rate constants. CCDC 1846694-1846696. For ESI and crystallographic data in CIF or other electronic forma

• Main Authors: Procházková, So a, Kubí ek, Vojt ch, Kotek, Jan, Vágner, Adrienn, Notni, Johannes, Hermann, Petr
• Format: Journal Article
• Published: 25.09.2018
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c8dt02608d

H 4 dota and its analogues are routinely used for complexation of lanthanide radioisotopes in nuclear medicine. Many of the radioisotopes have short half-lives and, thus, the complexation rate plays an important role. Notwithstanding that, the relationship between ligand structures and complexation rates is not well understood. Here we report a complexation study of H 4 dota and its analogues bearing one phosphonate or phosphinate pendant arm. The substituents on the phosphinate group were non-coordinating (-H) or contained another coordinating group (-CH 2 N(CH 2 COOH) 2 , -CH 2 PO 2 H 2 or -CH 2 NH 2 ). The basicity of ligands, stability of reaction intermediates, formation rates of Ce III complexes, and 177 Lu III radiolabelling were studied. The complexation rates and labelling yields do not show any correlation with ligand basicity. In contrast, the additional chelating group attached to the pendant arm plays an important role. A decreased complexation rate and lower labelling yield were found for compounds bearing an additional amino group, whereas improved properties were found for the compound bearing a geminal bis(phosphinate) pendant arm. It indicates that the introduction of chelating pendant arms with acidic coordinating groups might be a promising strategy to improve radiolabelling of macrocyclic carriers with metal radioisotopes. Highly acidic additional coordinating groups in the pendant arms increase the radiolabelling yield of DOTA-like complexes.